Removal Of Radiocesium Research Articles

湿式分級洗浄および天然鉱物等による農地土壌等に含まれる放射性セシウム除去方法の実践的検討

In the radiation dosimetry of radiocesium in Iitate, Fukushima, the level of radiocesium around the environment did not exceed the criteria in liquid phases such as puddle water, but was distributed in solid phases such as some soil types and organic matter. On the other hand, retting of the cut bamboo grass and hemlock fir in water allowed the release of radiocesium, about 230 Bq/kg exceeding the criteria for a bathing area. The flow-thru test using zeolite showed the removal of radiocesium from the liquid phase. The wet classification test was performed for 3 types of radiocesium-contaminated soil. According to the results of wet classification, radiocesium was detected and its level exceeded the cropping restriction level in almost all classified particle fractions. The decontamination effect of wet classification on radiocesium contamination was smaller than that on heavy metal contamination. Specifically, the wet classification could not induce volume reduction. Accordingly, preprocessing and intermediate treatments such as dispersion or attrition by vibration or mixing in the wet classification process were devised and examined as improved processing techniques. As a result, the effectual volume reduction of the radiocesium-contaminated soil was confirmed by adding an intermediate process such as the surface attrition in the vibrator.

Physicochemical Reasons for the Use of TiOHPO4 for Treatment of Liquid Radioactive Waste

Heterogeneous exchange of the proton of hydrated titanyl hydrogen phosphate with Li, Na, K, Rb, and Cs cations in aqueous solutions was studied potentiometrically. The sorption equations were proposed. The concentration and thermodynamic equilibrium constants were calculated. The optimal pH range of the solution providing effective sorption of radioactive cesium on hydrated titanyl hydrogen phosphate was determined. The decrease in the efficiency of radiocesium sorption from liquid waste with a high content of competing nonradioactive alkali metal cations is due to a decrease in the pH of this solution in the course of the sorption. To provide efficient sorption removal of radiocesium, the pH should be maintained in the range 4-7, or the sodium form of the sorbent should be used. The selectivity of radiocesium sorption on TiOHPO4 in the presence of excess sodium cation was estimated.

Supporting of some ferrocyanides on polyacrylonitrile (PAN) binding polymer and their application for cesium treatment

Abstract Transition metal ferrocyanides were supported on polyacrylonitrile (PAN) as a binding polymer and were used for removal of radiocesium. The sorption capacity was determined to be 1.22 and 0.55 mol g −1 for KZnHCF-PAN and KCuHCF-PAN, respectively. Different parameters affecting the sorption process were studied as chemical nature of the aqueous solution and flow rate of feed solution. The regeneration of the used sorbent was studied and also using the regenerated sorbents in other sorption cycles was studied up to four cycles.

Selective Removal of Cesium from Sodium Nitrate Solutions by Potassium Nickel Hexacyanoferrate-Loaded Chabazites

Potassium nickel hexacyanoferrate(II)s (KNiFC) were incorporated in the porous matrix of chabazite by successive impregnation with Ni(NO3)2 and K4Fe(CN)6. The loading percentage of KNiFC crystals on chabazite increased with repeated times of impregnation. The ion-exchange equilibrium of Cs+ in KNiFC-loaded chabazite (CFC) was attained within 2 days. Relatively large distribution coefficients of Cs+, K d,Cs, above 104 cm3/g were obtained, irrespective of coexisting NaNO3 concentration. There is a large difference between the K d value of 137Cs and those of other nuclides; the separation factor of Cs/Sr (αCs/Sr = K d,Cs/K d,Sr) was estimated to be above 104. The breakthrough curve for Cs+ through the column packed with CFC exhibited a symmetrical S-shaped profile, and this exchanger proved to be effective for the selective removal of radiocesium from waste solutions containing highly concentrated NaNO3.

放射線事故時におけるセシウム除去としてのプルシアンブルー

Prussian blue, a blue pigment, belongs to the ferric cyanoferrate (II) group. It binds univalent metal ions, and the binding activity depends on their ionic radius. Prussian blue is not absorbed from the gastrointestinal tract in a significant amount. The cesium is entero-enteric cycled through the intestine. Prussian blue inhibits the reabsorption of the cesium. Many studies using experimental animals showed that the oral administration of Prussian blue increases the rate of the fecal excretion of radiocesium which results in shortening its biological half life. The accident in Goiania, Brazil, in 1987 showed that Prussian blue effectively accelerated the removal of radiocesium without toxicity. In the present review, we describe Prussian blue from a biological aspect and discuss its clinical application for the decontamination of cesium in radiation accidents.

Removal of radiocesium from simulated alkaline salt loaded radwaste solution using potassium cobalt(II) hexacyanoferrate(II)

The inorganic sorbent potassium cobalt(II) hexacyanoferrate(II) was tested for removal of radiocesium from alkaline salt solutions that are typical of intermediate level radioactive wastes generated at spent fuel reprocessing plants in India. Excellent results were obtained both in batch equilibration and column operation.

Column Behaviour of Resorcinol-Formaldehyde Polycondensate Resin for Radiocesium Removal from Simulated Radwaste Solution.

The selective removal of radiocesium was studied using a column filled with resorcinol formaldehyde polycondensate resin (RFPR) prepared in the laboratory. The feed to the column was a simulated alkaline radioactive waste solution with high salt load of spent fuel reprocessing plant origin. Repeated loading-elution-regeneration cycles were conducted to determine reproducibility of breakthrough behaviour. The breakthrough data were correlated with batch equilibration data on cesium uptake. The quantitative elution of sorbed radiocesium was also confirmed.

In vitro binding of radiocesium to Prussian Blue coated strips and Prussian Blue containing hemoperfusion columns as a potential tool for the treatment of persons internally contaminated with radiocesium.

Cellulose or nylon strips coated with three different Prussian Blue salts were prepared with cellulose nitrate as binding material. These strips were evaluated for their usefulness for the development of an extracorporal clearance device for radiocesium, a radionuclide often released after accidents in nuclear installations (for example in Chernobyl). Extracorporeal clearance can be used to enhance the elimination of radiocesium from internally contaminated persons. The stability of these strips and their binding characteristics for radiocesium were investigated. In all studies strips coated with Fe4[Fe(CN)6]3 proved to be the most suitable for further development of an extracorporeal clearance device: the strips are stable, have a high binding capacity for radiocesium, and can be sterilized. On the basis of these results, hemoperfusion colums containing Fe4[Fe(CN)6]3-coated strips were developed and tested. In in vitro experiments these columns proved to be successful in removing radiocesium from a pasteurized plasma solution (clearance was approximately 100 ml/min). The binding capacity of these columns is relatively high. In 4 h the columns are able to bind approximately 0.3 TBq of radiocesium. They are a promising development for the enhancement of the removal of radiocesium from the human body. They can also be used for the decontamination of other fluids of chemical or biological origin. Further research is, however, still necessary.